The way i told my mom to use computer is...
just use it whichever way u wanted, if u have important information, send it to yourself via email (i get her a gmail account, and i learn from mistake that i SHOULD know her password) dont' keep anything important in your computer. and just USE it! browse whatever site u want.

having said that, my plan is.. if it got any adware, malware, virus, whatever ... all i am going to do is ... format/reinstall (i am actually planning to get a dummy harddrive and make an image of it. so i can just restore the image.
and of course, all my other computer block anything from her IP, in case she got worm.
one thing i would say is.. skip the history part... they won't care.... and i think it should be OS oriented (assuming will be M$ windows XP) just focus on ONE OS, and tell them how to boot up (or better, turn on the computer), how to hold the mouse, how to click, how to double click, click what to "go to the web", pick an email service and explain how to use icon by icon (unfortunately, in this case, i think hotmail will be better cuz you won't get question on how to get invitation from other gmail user!), how to read the content of a webpage (my mom did ask me what to do after she got to bestbuy's website! she just stare at the main page, and stucked!)... explain EVERY tiny detail that you and i might think is OBVIOUS/NATURAL!.
good luck on the book, once u done some preminliary work, i guess we (/.er) can comment on more!
PS: don't even bother explaining how great /. to them... Personally i am in an IC design company, which should be FILL with geeks, and i heard some ppl during lunch said /. is too geeky for them ..@~#@!#!!